PlainCities

Counties · Illinois

Counties of Illinois

Illinois has 102 counties. Cook County is the largest with 5,194,625 residents in 2025. 18 of the 102 gained residents between 2020 and 2025 by the Census Bureau's estimates.

What counties are in Illinois?

Sorted by the 2025 population estimate; sort by any column.

Counties of Illinois: 2025 estimate, change since 2020, ACS 2020-2024 5-year estimates
Cook County5,194,625−1.6%1611,332$83,498$324,500
DuPage County934,298+0.1%48219$112,096$391,400
Lake County719,339+0.7%78160$110,416$345,700
Will County712,253+2.1%83172$109,984$319,600
Kane County525,757+1.8%47104$103,163$327,000
McHenry County317,751+2.4%6064$104,802$308,100
Winnebago County283,674−0.6%2880$65,837$164,500
Madison County263,110−1.1%5663$75,793$173,000
St. Clair County250,708−2.7%5468$73,854$180,300
Champaign County209,972+1.7%5648$63,683$211,500
Sangamon County194,170−1.1%5254$75,357$176,300
Peoria County178,553−1.9%4149$65,108$158,500
McLean County171,419+0.1%5347$79,905$208,400
Kendall County145,470+10.3%2421$111,601$322,400
Rock Island County141,869−1.9%4243$67,159$150,400
Tazewell County130,049−1.1%3830$77,982$167,500
LaSalle County107,773−1.7%7028$73,045$161,900
Kankakee County105,525−2.0%3830$71,281$192,600
DeKalb County101,835+1.3%3323$70,724$243,600
Macon County99,300−4.5%3037$62,666$127,300
Vermilion County71,259−4.0%4224$56,877$97,200
Williamson County67,225+0.1%1918$65,604$156,400
Adams County64,267−2.2%4719$66,220$162,600
Whiteside County54,121−2.8%3519$67,500$127,100
Grundy County54,052+2.8%3410$92,235$271,700
Boone County53,568+0.2%1910$84,571$216,900
Jackson County52,501−1.6%2817$48,763$137,300
Ogle County51,399−0.9%4313$82,132$189,200
Henry County48,095−2.4%4314$71,911$151,600
Knox County47,767−4.4%3716$57,030$111,900
Coles County46,607−1.2%2013$56,478$127,400
Macoupin County43,748−2.9%5313$70,805$138,200
Stephenson County43,220−3.3%3113$64,043$134,900
Woodford County38,111−0.9%349$91,483$197,600
Clinton County37,128+0.6%319$86,588$192,400
Franklin County36,916−2.3%2912$56,740$89,000
Marion County36,382−3.6%3212$61,240$103,000
Jefferson County36,147−2.6%2711$63,118$126,000
Livingston County35,057−2.2%4610$73,790$142,200
Monroe County34,840−0.3%77$102,880$282,100
Effingham County34,519−0.4%258$80,404$189,500
Christian County33,443−1.8%3310$62,611$115,500
Lee County32,914−3.6%379$70,292$154,600
Fulton County32,901−2.3%4612$60,599$107,200
Morgan County32,515−3.1%1210$66,306$130,800
Bureau County32,510−2.3%5010$69,257$126,900
Randolph County29,921−0.8%1410$68,131$135,100
Montgomery County28,076−0.9%378$63,620$112,300
Logan County27,182−2.9%318$66,358$134,400
Iroquois County26,150−3.4%479$66,255$137,800
McDonough County25,916−4.9%3011$52,795$107,500
Saline County22,772−4.4%209$53,117$94,300
Jo Daviess County21,594−2.2%357$73,993$209,900
Jersey County21,160−1.7%196$80,361$171,900
Fayette County20,790−3.3%287$60,944$130,700
Shelby County20,576−2.0%386$72,095$137,100
Perry County20,160−3.7%66$62,118$112,600
Douglas County19,880+0.7%185$77,320$150,400
Crawford County18,648−0.0%186$71,674$121,100
Bond County16,959+0.4%194$65,959$145,700
Hancock County16,803−4.8%397$65,865$113,800
Piatt County16,791+0.6%194$94,811$180,600
Union County16,656−4.0%65$55,728$131,700
Edgar County16,323−3.3%235$59,941$97,300
Warren County16,222−3.7%225$67,385$105,000
Wayne County15,882−1.9%305$55,521$110,700
Carroll County15,419−1.9%206$60,758$114,500
Mercer County15,229−3.0%334$74,182$146,700
Richland County15,219−3.8%155$62,455$112,000
De Witt County15,118−2.5%215$71,678$130,300
Clark County15,114−2.4%204$72,927$132,400
Moultrie County14,371−1.1%164$71,784$134,000
Pike County14,231−3.4%425$59,777$101,400
Lawrence County13,790−9.9%145$55,324$99,100
Washington County13,564−1.5%304$78,224$155,700
Massac County13,502−4.8%34$65,116$121,900
Johnson County13,363+0.4%74$62,528$160,500
White County13,250−4.5%215$54,813$108,100
Ford County13,216−2.3%215$62,439$122,000
Clay County12,793−3.7%184$60,417$97,400
Cass County12,463−4.4%165$68,125$97,100
Mason County12,411−5.1%236$62,845$103,400
Menard County11,863−3.5%63$82,176$185,500
Marshall County11,473−2.4%215$71,585$142,800
Greene County11,313−5.5%225$62,192$95,200
Wabash County10,907−4.0%44$57,086$104,900
Cumberland County10,208−2.3%163$73,327$126,000
Jasper County9,032−2.9%193$74,755$125,500
Hamilton County7,859−1.7%173$65,746$113,700
Schuyler County6,657−3.5%173$65,948$109,700
Brown County6,401+2.5%132$67,917$150,300
Henderson County5,984−6.4%213$62,227$104,400
Edwards County5,898−5.5%53$60,519$100,000
Putnam County5,619−0.2%102$75,590$172,700
Stark County5,319−1.4%122$62,878$104,500
Scott County4,866−4.1%102$66,705$96,400
Pulaski County4,820−7.4%72$42,463$85,100
Gallatin County4,616−6.6%162$59,219$82,900
Alexander County4,570−12.8%74$47,043$59,800
Calhoun County4,300−2.9%52$93,203$190,900
Pope County3,672−2.5%22$60,050$143,800
Hardin County3,588−1.9%32$54,271$103,800

Source: PEP Vintage 2025 (CO-EST2025); American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) · Census population estimates

How these figures are made: methodology and release checks · reading a margin of error · every state · corrections